No one confirm than umbra will be inferior or equal to EP .
First, Why Umbra should be inferior or equal? Because that would make some people salty about it? There is now way since Umbra will be accessible by everyone by a quest. If there are still mad about that, that would be just selfish behavior.
Secondly. Prime variante have better stats than homemade tenno warframe (normal) yes, but no one can really confirm than prime variante made by orokin was the "best". Remenber, prime variante was the first warframe made by orokin, there a possibility they could made upgrade version or prototype like Umbra (Wich there are probably better and more advanced in many term).

My apologies but where did you get the information than Umbra is from dark side? Except the fact than stalker is using excalbur/excalibur umbra model and edgy propaganda. there is nothing that confirm Umbra is an "bad/dark side/ evil" warframe.
Also there is no way Sentient creat Umbra frame since warframe use void energy. which they are vulnerable.
Finally , I dont think DE will make Umbra or his influence as a moral choice because it would be disadvantageous for those who have made the wrong choices